Many food products are simply harvested and shipped directly to the consumer. This is common for fruit (pears, peaches, apples, grapes and so on) and it is also common for many vegetables. However, more and more benefits are obtained by processing harvested foods so that extracts are obtained from the foods. In the extraction process, the food is typically processed either by grinding or by preliminary cooking. In the first instance, many apples are crushed to extract the apple cider, and the pulp is subsequently processed for various derivatives sold in the market as apple butter, apple jelly, and the like. It is not uncommon to process potatoes to form similar products also. They typically are reconstituted in the form of extruded potato chips, french fries and other shapes and forms. It is also common to process a large number of grain crops. This typically requires some measure of processing to remove the husk or other parts of the plant which do not require processing. Thereafter, the kernel is processed typically by cooking to soften the kernel. To be sure, there is food value in an ear of corn, but it is generally hard and relatively unpalatable to the taste of most. Rather, the corn is at least separated from the shuck, and the kernels are removed from the corn cob. Thereafter, they may be processed by any number of subsequent cooking procedures. By crushing, corn starch can be derived. By appropriate pre-treatment and subsequent cooking, the corn can be converted by the hominy. The foregoing is also true of rice in that it has to separated from the husk and subsequently cooked.
In many of these procedures, whether cooking with elevated temperature or processing in other fashions, there is a waste discharge. The waste discharge is a water stream which carries in it some pulp from the processed fruit, vegetables and grain so that the treatment throws away a portion of the unconverted feed (the picked and ready to treat fruit, vegetable or grain).
The waste steam from a food processing plant is very difficult to treat downstream in a sewage system. It creates a tremendous oxygen demand. Ordinarily, food treatment plants have to pay a premium to dispose of this waste stream. The suspended particles or the sugars and starches in the solution pose a great burden on the treatment plant. As a practical matter, they also carry away a significant portion of the value in the feed materials. In a large plant, handling thousands of pounds per hour, this can be a various substantial discharge. More importantly, this discharge has additional utility costs in that it often is in the form of a water solution at substantial temperatures. Clearly, there is value to be obtained in extracting a substantial portion of the sugars and starches which are carried in the waste stream.
Take as an example a rice processing plant. The husk or hull is salvaged. It is obtained in a dry state. The next step of treatment involves cooking the rice. It is cooked in water and subsequently separated from that water. The water stream includes a very significant portion of starch or sugar derivatives. These are normally carried in suspension although a portion of it will dissolve into the water. It leaves a very difficult waste stream to handle. It is difficult to separate out any sediment in light of the volume is handled. Through the use of settling tanks, some portions can be removed, but the bulk of the food components remain suspended or dissolved in the waste water stream. The waste water is typically delivered at an elevated temperature. That tends to increase the amount entering into solution. Even where cooled to ambient temperature the waste stream is not easily segregated into a solid component retrieved from the segregated liquid component. By attempting to break the waste stream into the two components, some measure of improvement in the waste water post treatment steps can be obtained but it is a difficult chore to make this kind of separation.
The present disclosure sets out a method and apparatus for improved and enhanced treatment of food processing plant streams. It is particularly intended for use with those plants processing grains, fruit and vegetables. It is especially effective in the treatment of heated waste streams which are laden with bits of pulp, shredded skin (as would occur in an apple processing plant) and can recover components of substantial value. An example will be given below referring to a rice processing plant. The plant cooks the rice in water for a specified interval at elevated temperatures and then continues to treat the rice kernel after removing the kernel from the hot water. The hot water stream (otherwise a waste product stream) is input to a system for improving the post cooking treatment of the spent hot liquor using that term to apply to the waste water laden with pieces of the grain, fruit or vegetable either in solution or in suspension or both. The waste stream is delivered to a processing plant in which the water is extracted for easy disposal. The stream of water after treatment places minor demands on the sewage system. This water is clarified and otherwise stripped of the derivatives from the fruit, vegetable or grain treated in the plant. Collectively, the input will be termed the "liquor" and the liquor is broken down into two components by the treatment process and is discharged as the clarified solvent (practically always water) while the recovered components will be described generally as the extract. The extract is comprised of some pulp from the liquor and includes a significant portion of starches and sugars.
Within this context, the present method and apparatus are summarized as a disposal system for food processing plant to handle the discharged liquor from the process. This stream which is otherwise wasted includes the solvent and relatively valuable food components which are recovered. This recovery approach uses a combination membrane filtration in conjunction with centrifuge separation. Interestingly, it has been found that the recovery is markedly enhanced by combining the two procedures in conjunction with a feedback flow so that reprocessing is carried out in a continuous fashion, and the achieved results are controllably executed in a combined system. With appropriate pumps, flow tanks and measuring instruments, a control system is implemented so that the flow of the food plant liquor is appropriately processed to make this valuable recovery. Better than that, the discharged water from this process is more easily disposed, and is not laden with the excessive food plant components which otherwise have such a high oxygen demand in subsequent processing as sewage.